Residual properties of conventional concrete repetitively exposed to high thermal shocks and hydrocarbon fluids

The rapid degradation of traditional concrete at aprons in army airbases is a major problem for the operation of jet aircraft safely. Aprons are often saturated by rainfall water and hydrocarbon fluids (HFs) and are frequently subjected to heat shocks from jet exhaust. The current study investigates the causes of rapid degradation of airbase concrete and the effects of that on concrete properties. Standard sized concrete cylinders (w/c ratio = 0.35, 0.45 and 0.55) using Australian general-purpose cement were prepared and repeatedly exposed to both high thermal shocks and HFs, separately and combined until degradation becomes obvious in term of surface scaling. Surface scaling was developed when cylinders were subjected to the coupled effects of high thermal shocks and HFs, cylinders did not form scaling when subjected to high thermal shocks and HFs individually. However, significant changes in residual properties were identified for all exposure types. The considered cylinders showed 40% of decrease in the compressive strength and more than 27% of decrease in the splitting tensile strength. In addition, the elasticity of concrete was reduced by more than 63% after the formation of scaling on the surface. The crystal lattices of minerals in cylinders, such as alite, belite, quartz, ettringite, portlandite, and mullite were significantly decomposed owing to the repetitive actions of both thermal shocks and HFs combined, which resulted in the deterioration of mechanical properties. Deterioration of mechanical properties of cylinders highly depended on w/c ratio. Cylinders with a lower w/c ratio retained the higher percentage of residual strength when subjected to the coupled effects of high thermal shocks and HFs. This study also reports the influence of w/c ratio on mass loss characteristics and microstructures of conventional concrete subjected to both thermal shocks and HFs simultaneously. (C) 2020 Elsevier Ltd. All rights reserved.